1. Field of the Invention
The instant disclosure relates to a DC-based uninterruptible power system; in particular, to an abnormal voltage detection method used for the DC-based uninterruptible power system.
2. Description of Related Art
In recent years, personal computer, communication equipment, workstations and other kinds of hardware equipment are widely used in all level of society with the rapid development of information industry. As information itself is a high value-added product, so people find ways to ensure safety of information and the normal operation of the computer system, and requirement for the power quality have become increasingly strict. Since a large number of power electronic equipment are be used, harmonics generated from power electronic equipment cause poor power quality and natural disasters, and further result in utility power not to guarantee a stable supply of high-quality. Uninterruptible power supply system (UPS) immediately become indispensable equipment for computer or communication system.
UPS can avoid data loss and damage of the electronic device resulted from power anomalies, and can effectively protect the internal component of electronic device to ensure the life and precision of electronic device. In addition, when an emergency power fails (e.g., a sudden power failure), can also to be the buffer time on shutdown. Currently, UPS on the market are mostly external; which means, UPS is disposed outside the host independently, and is electrically connected to electric wire of the host. Generally, UPS have discharge mode and non-discharge mode, and a means to switch two modes is through detecting the supply situation of the output-side, so as to determine switch two modes, so how to detect supply situation precisely and quickly is important. In real application, in order to meet effect of outputting the high-current output immediately, a linear regulator usually maintains open-state, and be with another switch element (e.g., MOS) to avoid DC current to return. However, when UPS is in non-discharge mode and the linear regulator maintains open-state, current will flow to the output-side through a conduction of a body diode of the MOS so that an voltage comparator does not detect supply situation of the output-side quickly and loss of an power energy happens in the non-discharge mode. Accordingly, a battery of the UPS needs to be charging frequently so as to significantly reduce life of battery.